<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>04_JS的流程控制</title>
</head>
<body>
    <script>
        //1.顺序结构
        console.log(1);
        console.log(2);
        console.log(3);

        //2.分支结构
        var age = 18;
        if(age >= 18){
            console.log('可以投票');
        }else{
            console.log('不可以投票');
        }
        let uname='linda';
        if(!uname){
            alert('请输入用户名！');
        }else{
            // alert('欢迎登录！'+uname);
        }

        //3.选择分支
        let gender=1;
        switch (gender){
            case 1:
                console.log('男');
                break;
            case 0:
                console.log('女');
                break;
            default:
                console.log('未知');
        }

        //4.循环结构
        let names = ['linda','lucy','lili'];
        for(var i=0;i<names.length;i++){
            console.log(names[i]);
        }
        console.log('循环结束');
        //如果用var定义循环变量i，循环结束后在此处仍能打印出i的值
        //但如果用let定义i，就会报错：ReferenceError: i is not defined
        console.log(i);

        //5.增强for循环
        //n是每轮遍历从names数组中取出的元素
        for(let n of names){
            console.log(n);
        }
    </script>
</body>
</html>